A last-ditch plea for clemency is being prepared on behalf of a British businessman held for 20 years in a Florida jail.

The move follows unsuccessful attempts to win a retrial in spite of evidence suggesting his conviction of a double murder was a miscarriage of justice.

Krishna Maharaj, a 67-year-old businessman from London, was convicted for the 1986 murder of a Jamaican father and son in a hotel room in Miami, Florida and has already served 20 years in a US jail.

Maharaj - who spent the bulk of his time in prison on Death Row - has always protested his innocence.

Two years ago a Newsnight investigation unearthed new information that raised doubts about the reliability of the two key prosecution witnesses, whose testimonies were critical in putting Maharaj behind bars.

Alibi witnesses

The investigation also traced one new alibi witness, and asks questions about why five other alibi witnesses - all placing Maharaj 30 miles away from the scene of the crime at the time of the murders - were never called to testify.

The findings suggest Krishna Maharaj is the victim of a miscarriage of justice and add credibility to theories that he was framed for the murders.

One of the prosecution witnesses, Jamaican Tino Geddes, originally provided an alibi for Krishna Maharaj but changed his story on the eve of the trial in 1987 to say that the Londoner had planned the murders.

But now Tino Geddes has revealed to the BBC information which raises questions over his reliability as a witness.

At the time of the trial, Geddes was himself facing a criminal trial for bringing ammunition into Jamaica from the US; a charge which could carry a jail sentence.

The Maharaj case prosecutors flew to Jamaica and assisted Geddes in the case.

Mr Geddes testimony was crucial in putting Maharaj behind bars

Tino Geddes also revealed that the authorities helped him with a charge for driving under the influence of alcohol - and that the prosecutors went to a lap-dancing bar with their star witness.

"If the jury had really got the story about how Tino was getting favours from the government it would have made them look very differently at Tino," said Maharaj's British defence lawyer Clive Stafford Smith.

Lie detector test

Further doubts emerged about the second key prosecution witness, Neville Butler, who was the only apparent eyewitness to the crime, and also critical to Krishna Maharaj's conviction.

There are real reasons for thinking that he [Maharaj] may have been framed, that crucial evidence about the principal prosecution witness may not have been disclosed, indeed was not disclosed

Former Attorney General Sir Nicholas Lyell QC

Maharaj's defence team claim that Neville Butler failed part of his lie-detector test (Maharaj passed his) and that his account is riddled with inconsistencies, such as changing versions of who booked the hotel room where the murders took place.

In the Bahamas, the BBC spoke to a tour operator, Prince Ellis, who says he saw Butler on the day of the murders.

Prince Ellis told Newsnight, he spent the evening with Butler and another man Eddie Dames.

Mr Ellis claims Butler had blood on his shirt, had never mentioned Krishna Maharaj's name once during the evening, and was told by Mr Dames to get his "story straight" before going to the police.

Mr Ellis also says Butler implied that more than one person was involved in the shooting - contrary to his account in court that Maharaj had acted alone.

Krishna Maharaj has always maintained that at the time of the murders in Miami, he was 30 miles away in Fort Lauderdale.

Indeed, all the five alibi witnesses have stated that he was in Fort Lauderdale at the time - yet not one of them was called to testify at his trial.

Judge arrested

But this was no ordinary trial: the judge was arrested and led away in handcuffs after three days on suspicion of taking bribes in another case.

During its investigation, Newsnight traced one new alibi witnesses, a woman who then spoke out for the first time.

She said she saw Krishna Maharaj in Fort Lauderdale twice during the time when the state says the murders occurred in Miami - between 11am and noon on 16 October 1986.

The room where Derrick Moo Young and his son Duane were killed

When asked whether it was feasible that sometime between 11am and noon Krishna Maharaj could have been in downtown Miami committing murder, she replied: "No, it's not. No, it's not. Absolutely not."

The BBC also tracked down Adam Hosein in Trinidad who Maharaj's defence lawyers think has some serious questions to answer in this case.

A former employee of Hosein, George Abchal, claims that on the day of the murders Mr Hosein said he was going to the hotel where the killings occurred.
Mr Abchal also claims a gun and silencer were missing from Mr Hosein's drawer and that night he told him he had "eliminated" a few people.

The man has never been questioned by the police in relation to this case.

Re-trial battle

Some 300 British politicians from all the main parties supported his quest for a retrial - including a former UK attorney general.

The former Attorney General Sir Nicholas Lyell QC has been one of those advocating a retrial.

Sir Nicholas, who for five years was the government's chief legal officer, told the BBC at the time of its investigation:
"There are real reasons for thinking that he may have been framed, that crucial evidence about the principal prosecution witness may not have been disclosed, indeed was not disclosed, that he was inadequately represented, that the case was handled by a judge who in the middle of the case was arrested and subsequently disbarred.

"And that there are real reasons for all those reasons to think that this is a grave miscarriage of justice which one would hope can be put right."

But for all the evidence suggesting a miscarriage of justice, Krishna Maharaj has been unable to win a re-trial, and last week the Supreme Court refused to take the case, exhausting his legal avenues.

A plea for Clemency is being prepared for the Florida Governor Jeb Bush by Maharaj's political and legal supporters.

Four years ago, after spending more than 15 years on Death Row, his sentence was commuted to 50 years in jail - because of judicial impropriety in his original trial.

Tim Samuels' latest report for Newsnight can be seen on Monday, 16 October, 2006 at 10.30pm on BBC TWO.